The cleaning and sterilization of complex endoscopic surgical instruments presents a major problem in achieving a repeatable standard of both cleanliness and biocidal safety.
As the endoscopic instruments used in “key hole surgery” are expanded to cover more types of interventional conventional surgery, new instruments are becoming more and more complex in construction and therefore more difficult to maintain between surgical procedures.
Unfortunately, current endoscope detergents have a problem with foaming under higher pressures. As the complexity of surgical instrument construction has evolved, so has the need for increased miniaturization of tubing systems, through which surgical lighting, instruments, fluids and air are fed to the surgical interface, which has presented problems associated with cleaning efficiency. Cleaning under higher pressures has seen problems associated with reduced cleaning performance which has been further complicated by the need for mechanical cleaning and sterilizing of these complex instruments at temperatures as high as 55° Celsius.
Even further complicating the cleaning procedures is the existence of tenacious and resistant biofilms deposited by bacteria and viruses that enter tubing from the surgical interface. This is particularly the case where surgical instruments have been used to obtain a biopsy from an infected or degenerated wound. Here the contamination may be by bacteria, bacterial spores, fungi, or viruses.
While new high pressure cleaning and sterilizing techniques increase biofilm removal rates, the complexity of circulating systems in endoscopes leads to foam development from surfactants commonly found in the cleaning and sterilizing products used. Foam generated during reprocessing seriously impedes cleaning and biofilm removal.
Thus far, no detergent cleaning product or chemical sterilant has been developed that is both effective as a chemical sterilant and non-foaming under the high pressures exerted within the endoscope tubing and channels during reprocessing.
Existing glutaraldehyde chemical disinfectants, which are commonly used after precleaning with an appropriate medical detergent such as described in WO 02/07789 (inventor R K Whiteley), are an important, effective and economical way of achieving the desired level of disinfection of endoscopes and related instruments. Existing glutaraldehyde chemical compositions include those described in U.S. Pat. No. 4,748,279 and U.S. Pat. No. 6,525,101 (inventor R K Whiteley). However, these existing surfactant compositions suffer from the preceding limitations.
The presence of foam during reprocessing of endoscopic instrument is undesirable as it impedes chemical cleaning and disinfection. The propensity of surfactants to form foams is a distinct area of surfactant science, a subject which is explicitly detailed in terms of physical chemistry and interfacial behaviour discussed in the book by R. Pashley & M. Karaman “Applied Colloid & Surface Chemistry”, Wiley press 2004.
Where foams due to surfactants are undesirable, it may be possible to incorporate a small quantity of a second surface active molecule to disrupt the orderly arrangement thus destroying its mechanical stability. This gives a temporary reduction in foam which is often adequate for specific applications. Anti-foam chemicals are also temporary in action and become progressively inactive when solution is reused many times due to the introduction of biological soils (foreign matter).
Surfactants (surface active agents) which are classified as non-foaming are unable to form stable foams because they cannot uniformly pack at the air/water interface. Rather than the surfactant molecules aligning at the air/water interface into a well packed surface layer these surfactants usually have large branched chained moieties which find difficulty in packing at the air/water interface, therefore they have a tendency to lay irregularly across the air/water interface and hence lack the potential to form mechanically stable surface layers. These molecules consequently are unsuitable for formulating disinfectants, chemical sterilants and chemical biocides.
A further method of foam suppression is the addition of a small quantity of a surfactant with a high charge on the hydrophile that is incompatible with that of the primary surfactant. Here the free, more ionized, surfactant molecules compete aggressively for a position at the air/water interface, thereby preventing formation of a stable spatial interfacial surfactant arrangement. The second surfactant contributes little, if anything, to the lowering of the air/water and oil/water interfacial tensions, being totally ineffectual in this latter regard. Foam control is temporarily being readily affected by incoming soil.
The above discussion of background art is included to explain the context of the present invention. It is not to be taken as an admission that any of the documents or other material referred to was published, known or part of the common general knowledge at the priority date of any one of the claims of this specification.
There is a need for a composition which effectively cleans and sterilizes endoscopic surfaces, preferably to a higher standard than is currently achieved. It would be desirable for the composition to be effective at conditions present in washer-disinfectors circulating conditions, which include high temperature (around 35°-55° C.) and high pressure. In particular, the composition must effectively clean and sterilize at temperatures up to 55° C. and high pressure the narrow channels and lumens where fluids and air and/or vacuuming occurs in the endoscopic equipment. Most particularly, the composition should form little or no foam so as to overcome the difficulties encountered with existing compositions during cleaning and sterilising procedures, particularly when cleaning and sterilising endoscopic surgical equipment and instruments.